Mineral insulated conductor workpiece



Dec- 25, 1951 E. G. L. ROBERTS MINERAL INSULATED CONDUCTOR WORKPIECE Filed Oct. l5. 1947 fdffrfdfdu GA MMA ALUM/NA TUBE Patented Dec. 25, 1951 NITED 'STATES ,le rieur f Acertes VMINERAL,IlszrsULA'rlfzn CONDUCTOR WORKPIECE Edwin Gilbert Llewellyn Roberts, Bolton, England Application October 15, 1947, SerialNo. 779,912 -In Great Britain Octcber: 24, 1946 l Claims. 1

This invention relates to fthe manufacture of 'The object of the present-:invention is 'to 'pro- `Vvide an article of manufacture which will overycome 'the fobjections referred to. the present invention -the article of manufacture comprises in combination a lmetal tube, a granu- According Vto lar dielectric crypto-crystalline:material consisting of gamma alumina filling the metal tube, the

granular `dielectric crypto-crystalline material being isotropic land amorphous and ,possessing plastic and fluid properties, land means closing vat both ends themetal tube filledwith the granular dielectric crypto-crystalline material.

In the accompanying drawing which illustrates one embodiment of this invention:

Figure 1 is a vertical section of a tubular body tted with a pair of conductor rods.

Figure 2 is a similar view illustrating the body partially lled with insulating material or dielectric, and the ram used for pressing the same into a compact condition.

Figure 3 is a similar View illustrating the body filled to the desired extent and with a metallic sealing disc in position, and

Figure 4 is a similar view illustrating the means for closing the end of the tubular body over the top of the sealing disc and for bringing the insulating material up to the required density for its occupied volume.

In the drawings, which illustrate an embodiment of the invention as applied to a work-piece provided With two conducting rods designed in the completed conductor to be insulated from each other, the work-piece comprises a metallic tube or bottle I the closed end 2 of which is drilled and tapped to receive the threaded ends of the conductor rods 3 suitably spaced apart. The open end of the tube I is bevelled as at 4 on the inside for the purpose hereafter described.

In carrying out this invention the work-piece comprising the tube l and conductor rods 3 is loaded with insulating material or dielectric 5 consisting of gamma alumina, which material as before stated is isotropic or amorphous, and is in a granular form, such material being hereinafter referred to as the dielectric material. After a given quantity of material has been fed into the tube it is partially consolidated in situ by a suitable ram 6 provided on its lower end with a die l.

/Then the vram is 'withdrawn and'further quantitie'sof the dielectric are fed in-and'p'arti'ally consolidated until the tube is practically filled, Iallowing suicient length at the open end, as illustrated in Figure 3, "to permit 'a metallic disc 8 suitably drilled to vbe placed overthe conductors 3, and, by1afxing a suitably formed die 9 on tothe Vend -of the ram 6to lclos'e over onto said disc the bevelled en'd 4 of the tube and `thereby lock the 'sealing `disc v3 firmly in position on top of the ldielectric material 5, said dielectric material being simultaneously consolidated to maximum density for its occupiedvolume by pressure. T-h'e dielectric material is normally obtained incommercein the 'form of alin'ely divided powden-and requires treatment before it is suitable for the purposes of Amy invention. A convenient method of bringing the flnely divided powder into the .granular form -is first to agglomerate the same by dry pressing or moulding as is common in ceramic technique and then to disintegrate the same by a crushing operation designed to reduce it to an aggregate so that the particles will pass through a circular aperture of approximately onequarter of an inch in diameter. The completed work-piece can be drilled with small holes at both ends to enable the free egress of Water (if any) vapour and gases, when it is heated. In cases where hot rolling of the work-piece is required, said work-piece can be either dried to expel the mechanically held or chemically combined Water and occluded gases previous to heating to the necessary temperatures required to roll it in the hot condition, or, it can be slowly heated up to that temperature in one operation. Such rolling temperature ranges from 800 to 900 C. in the case of copper sheaths and conductors.

What I claim is:

l. An article of manufacture adapted to be used as initial work-piece in a, process for the manufacture of metal clad mineral insulated conductors by the reduction in cross-section of such initial work-piece, said article of manufacture comprising in combination, a metal tube; a granular dielectric crypto-crystalline material consisting of gamma alumina lling said metal tube, said granular dielectric crypto-crystalline material being isotropic and amorphous and possessing plastic and fluid properties; and means closing at both ends said metal tube lled with said granular dielectric crypto-crystalline material.

2. An article of manufacture adapted to be used as initial Work-piece in a process for the manufacture of metal clad mineral insulated conductors by the reduction in cross-section of such initial work-piece, said article of manufacture comprising in combination, a metal tube; granular gamma alumina filling said metal tube; and closing means closing at both ends the metal tube filled with said granular gamma alumina.

3. An article of manufacture adapted to be used as initial work-piece in a process for the manufacture of metal clad mineral insulated conductors by the reduction in cross-section of such initial work-piece, said article of manufacture comprising in combination, a metal tube being open at one end and composed of a metal cylindrical Wall and a metal end Wall provided at one end of said metal cylindrical wall and forming one unitary structure with said metal cylindrical Wall of said metal tube closing the same at its other end; a granular dielectric crypto-crystalline material consisting of gamma alumina filling said metal tube, said granular dielectric cryptocrystalline material being isotropic and amorphous and possessing plastic and fluid properties; and closure means closing said open end of said metal tube lled with said granular dielectric crypto-crystalline material.

4. An article of manufacture adapted to be used as initial Work-piece in a process for the manufacture of metal clad mineral insulated conductors by the reduction in cross-section of such initial work-piece, said article of manufacture comprising in combination, a metal tube being open at one end and composed of a metal cylindrical Wall and a metal end wall provided at one end of said metal cylindrical Wall and forming one unitary structure with said metal cylindrical wall of said metal tube closing the same at its other end; a granular dielectric crypto-crystalline material consisting of gamma alumina filling said metal tube, said granular dielectric crypto-crystalline material being isctropic and amorphous and possessing plastic and uid properties; closure means closing said open end of said metal tube lled with said granular dielectric crypto-crystalline material;

' at least one lopening in said closure means; and

at least one core arranged within said metal tube extending in longitudinal direction thereof 'secured at one end to said metal end Wall of said metal tube and passing at its other end through said opening in said closure means closing said open end of said metal tube.

EDWIN GILBERT LLEWELLYN ROBERTS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date" 573,176 Borel Dec. 15, 1896 1,127,281 Read Feb. 2, 1915 1,157,916 Wentworth Oct. 26, 1915 1,192,457 Read July 25, 1916 1,279,252 Capp Sept. 17, 1918 1,809,089 Wiegand June 9, 1931 1,993.580 Abbott Mar. 5, 1935 2,091.839 Tangeman Aug. 31, 1937 2,123,778 Heilmann July 12, 1938 2,279,726 Allen Apr. 14, 1942 2,431,474 Gandenzi Nov. 25, 1947 OTHER REFERENCES Tomlinson et al.: Publication entitled Mineral- Insulated Metal-sheathed Conductors; Journal of the Institute of Elect. Engrs.; August 1946; pgs. S25-340; pg.325 in particular relied upon. Copy in Div. 65. 

